As is known, a typical mill, for example, has a rotating spindle provided with a tapered, smooth bore for receiving a comparably tapered shank or tang of a tool such as a line bar or the like. In conventional construction, cooperative crosswise slots in the shank and spindle are provided, and these slots, although partly alined, are axially offset. In a vertical attitude, the bottom of the spindle shank is spaced below the top end of the shank slot. It is commonplace to manually force a wedge between the aforesaid slot portions for compelling the shank to move upwardly and thus more tightly into the spindle bore.
According to the present invention, a novel form of expandable keeper is provided, which is a relatively small, compact unit having screw-actuated cooperative cam members or ramps for exerting the tightening force. The unit is of simple design, preferably made of suitable steel parts that are few in number and so arranged as to be substantially mutually cooperative in keeping the unit assembled and thus preventing loss of its parts. More specifically, the unit comprises a base having at one end an upstanding anchor to which is pivoted a tongue having an undersurface in the form of a cam adapted to ride on a ramp formed on a block carried by the block for movement lengthwise thereof toward and away from the anchor, the movement being controlled by a screw which, when turned in one direction, draws the block toward the anchor and causes the tongue to ride upwardly. The block engages the bottom of the spindle slot and the tongue engages the top of the shank slot.
It is a feature of the invention that the size of the unit is such that it fits readily into the spindle and shank slots without projecting beyond the circumference of the spindle. The pivoting of the tongue is such as to embody a retaining function as respects the screw, eliminating the need to provide a bore in the anchor to which the tongue is pivoted. Further, the bottom of the tongue, in addition to being formed as a cam, has a groove that at least partly engages the screw loosely from above, thus further adding to the alinement of the screw and ramp block with the base. A stop is provided on the base to prevent escape of the block during loosening rotation of the screw.
The foregoing and other features and advantages of the invention will become apparent from the ensuing description of a preferred embodiment of the invention, taken in conjunction with the accompanying sheet of drawings.